Many electronic devices that are currently widely used include a touch panel. Information can be input to an electronic device with the touch panel by directly touching the touch panel with a finger or the like. The touch panel is expected to be further widely used as a simple data input unit.
Incidentally, most typical touch panels detect a contact position when 1 point of the touch panel is being contacted. Therefore, in a case where the touch panel is being contacted at 2 points or more, position of the contact points cannot be detected accurately. Therefore, there is a desire for a method that allows accurate position detection even in a case where the contact points are two points.
As for a method of detecting contact points in a case where the contacts points are two points of the touch panel, various methods are disclosed in the following Patent Documents 1 to 17.
More specifically, there is disclosed, for example, a method of using the slight difference between the time of contacting the first point and the time of contacting the second point, a method of connecting a resistance to a conductive film of a touch panel, and a method of applying a voltage between an X side electrode and a Y side electrode.
Further, in the following Patent Document 12, there is disclosed a method of detecting distance information between 2 points in a case where 2 points are depressed. Further, in the following Patent Document 14, a configuration having a divided resistance film is disclosed. Further, in the following Patent Document 17, a configuration having 2 sets of resistance films is disclosed. Further, in the following Patent Documents 18 and 19, there is disclosed a method that corrects distortion caused by contacting 1 point.    Patent Document 1: Japanese Registered Patent No. 3402858    Patent Document 2: Japanese Laid-Open Patent Publication No. 2009-289157    Patent Document 3: Japanese Registered Patent No. 3397519    Patent Document 4: Japanese Laid-Open Patent Publication No. 8-54976    Patent Document 5: Japanese Laid-Open Patent Publication No. 3-77119    Patent Document 6: Japanese Laid-Open Patent Publication No. 10-171581    Patent Document 7: Japanese Laid-Open Patent Publication No. 11-95929    Patent Document 8: Japanese Laid-Open Patent Publication No. 1-269120    Patent Document 9: Japanese Laid-Open Patent Publication No. 8-241161    Patent Document 10: Japanese Laid-Open Patent Publication No. 8-54977    Patent Document 11: Japanese Laid-Open Patent Publication No. 2007-156875    Patent Document 12: Japanese Laid-Open Patent Publication No. 2009-176114    Patent Document 13: Japanese Registered Patent No. 3351080    Patent Document 14: Japanese Laid-Open Patent Publication No. 9-45184    Patent Document 15: Japanese Laid-Open Patent Publication No. 2005-49978    Patent Document 16: Japanese Laid-Open Patent Publication No. 2010-102627    Patent Document 17: Japanese Laid-Open Patent Publication No. 11-232023    Patent Document 18: Japanese Laid-Open Patent Publication No. 2001-67186    Patent Document 19: Japanese Registered Patent No. 2554577    Patent Document 20: Japanese Laid-Open Patent Publication No. 2011-76591    Patent Document 21: Japanese Laid-Open Patent Publication No. 2011-123815    Patent Document 22: Japanese Laid-Open Patent Publication No. 2011-134316
With the above-described method of detecting the position information of 2 contact points of the touch panel, there is a problem of being unable to accurately detect position coordinates of 2 points in a case where the 2 points are contacted simultaneously. Further, the configuration of dividing the resistance film for detecting 2 points or the configuration of providing 2 sets of resistance films for detecting 2 points require a specific structure and lead to increase of manufacturing cost.
Therefore, there is a desire for a position detection method that allows position coordinates to be detected with a conventional 4-wire type touch panel at a low cost even in a case where 2 points are simultaneously contacted.